Does the Fine-Tuning of the Universe Point to God?

The Short Answer

Physicists of every belief agree that many of the basic constants and starting conditions of the universe fall within narrow ranges that allow complex chemistry, stars and life to exist. Change some of them only slightly and, as far as we can tell, there would be no stable atoms, no long-lived stars, no life. There are three broad explanations: chance, physical necessity, or design. Catholics hold that design is the most reasonable of the three. The argument does not prove the God of Christianity, but it adds weight to the conclusion that the universe is the work of a mind.

Critics reply that the argument is a “God of the gaps,” that we would not be here to notice otherwise, or that there are countless universes and we live in a lucky one. These are serious replies, and they deserve a fair hearing.

What the Church Does and Does Not Claim

The Church does not claim:

That fine-tuning is a doctrine of faith. It is a philosophical argument built on scientific findings. If the science changes, the argument changes with it; the faith does not.
That the numbers are settled. Physicists debate how many constants are really fine-tuned, and how finely. Some popular figures are overstated.
That the argument proves the Trinity or the Gospel. At most it points to an intelligent cause of the universe.
That God is needed only where science runs out. God is the Creator of the whole of nature, including the laws science studies.

The Church does claim that God can be known “with certainty from the created world by the natural light of human reason” (CCC 36), and that the order of the world reflects the wisdom of its Creator: “you have arranged all things by measure and number and weight” (Wisdom 11:20).

Why Catholics Find It Persuasive

What physicists have found

A few examples, all widely discussed in the scientific literature:

The cosmological constant, which governs the expansion of space, is extraordinarily small compared with what physicists’ best theories would naively predict. On one common estimate the mismatch is around 120 orders of magnitude. If it were much larger, matter would have flown apart before galaxies and stars could form.
The strength of the strong nuclear force, which binds atomic nuclei. Changes of a few per cent, by many calculations, would upset the balance that allows both hydrogen and the heavier elements needed for life.
The masses of the neutron, proton and electron, which sit in a narrow window that allows stable atoms and long-lived stars.

The astronomer Fred Hoyle, for most of his life an atheist, was struck by how precisely the nuclear physics of stars allows carbon to form. He concluded that a commonsense reading of the facts suggests “a superintellect has monkeyed with physics, as well as with chemistry and biology” (“The Universe: Past and Present Reflections,” 1981).

For a careful, recent account by two working cosmologists, one a believer and one not, see Geraint Lewis and Luke Barnes, A Fortunate Universe (2016).

Three explanations

Chance. The values just happen to be right. That is possible, but when the odds are as long as the physics suggests, chance is a weak explanation. If a hundred marksmen all miss you at point-blank range, “I wouldn’t be here to wonder otherwise” is true, but it does not explain why they missed.

Necessity. Perhaps a deeper theory will show that the constants could not have been otherwise. No such theory exists yet. And even if one were found, it would raise the next question: why are the deepest laws such that they produce a life-permitting universe?

Design. The universe looks fine-tuned because it was made by a mind with a purpose. This is not an appeal to ignorance but an inference to the best explanation, the same kind of reasoning we use whenever we recognise intelligence at work. Scripture says the same in its own way: “The heavens are telling the glory of God; and the firmament proclaims his handiwork” (Psalm 19:1). Isaiah says God “did not create it a chaos, he formed it to be inhabited!” (Isaiah 45:18).

Common Objections

”This is just a God of the gaps.”

A “God of the gaps” fills holes in our scientific knowledge, and shrinks as science advances. The fine-tuning argument works the other way round. It does not point to something science cannot explain; it points to what science has discovered, and asks why the laws science describes are what they are. That question does not shrink as physics grows.

”If the universe weren’t fine-tuned, we wouldn’t be here to notice.”

True, and it explains why we observe a life-permitting universe rather than some other kind. It does not explain why a life-permitting universe exists at all. The marksmen example still applies.

”There are countless universes. We are in one of the lucky ones.”

The multiverse is taken seriously by many physicists, and Catholics need not fear it. But as an answer to fine-tuning it has limits. There is at present no direct evidence for other universes. A mechanism that produces many universes with varying constants would itself need the right laws to work, so the question of fine-tuning moves back a step rather than disappearing. And a multiverse, if it exists, would still be part of creation, depending on God for its existence. The Catholic position does not hang on there being only one universe.

”Life adapted to the universe, not the other way round.”

Evolution explains how living things adapt to their environment. But fine-tuning concerns whether there could be any environment for life at all: stable atoms, long-lived stars, chemistry. Without those, there is nothing for evolution to work on.

In Summary

Modern physics has found that the universe’s laws and starting conditions fall within surprisingly narrow ranges that allow life. Chance and necessity are possible explanations, but neither is satisfying. Design is the most natural reading, and many scientists, believers or not, have felt its force. The argument does not prove the Christian faith, and its details are still debated. But it fits what Scripture and the Church have always said: that the world is the work of a wise Creator who made it to be inhabited.

This article follows the method St Robert Bellarmine used in his Controversies*: state the question fairly, clear away misunderstandings, make the case, then answer each objection. See How We Answer Objections.*

Sources

Scripture: Revised Standard Version, Second Catholic Edition (Ignatius Press). Psalm 19:1; Wisdom 11:20; Isaiah 45:18.
Catechism of the Catholic Church, nn. 31–36, 295–299.
Geraint F. Lewis and Luke A. Barnes, A Fortunate Universe: Life in a Finely Tuned Cosmos (Cambridge University Press, 2016).
Fred Hoyle, “The Universe: Past and Present Reflections” (1981). todayinsci.com